


A Sudden Change of Heart

by orphan_account



Category: Undertale (Video Game)
Genre: Angst, Gen, Genocide Run, Mpreg, Pregnancy, lmfao i could have written this better im so sorry, skelepreg, worst possible timing
Language: English
Status: Completed
Published: 2016-01-13
Updated: 2016-01-25
Packaged: 2018-05-13 18:41:39
Rating: Teen And Up Audiences
Warnings: Major Character Death
Chapters: 2
Words: 5,374
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/5712997
Author URL: https://archiveofourown.org/users/orphan_account/pseuds/orphan_account
Summary: <blockquote class="userstuff">
              <p>Using too much magic is bad for an expectant mother's health.</p>
            </blockquote>





	1. It's All Over

Sans paced around the hallway that led to the King’s throne room; anxious was putting it lightly, he seemed to be suppressing the urge to have a breakdown by this point. Had the circumstances been different, perhaps he would be more willing to accept what he was about to do, but his hands were dug deep into his coat pockets, rubbing at his swollen belly.

Almost around a day or two ago, Sans was coming ever so close to his due date, he never really thought he would become a parent at some point in his life, but the idea wasn’t too outlandish. He thought it might be nice really, just to settle into the family way and while it has been rather trivial given the stress it put on him, he did come to terms with it and even took some initiative to prepare for the child’s arrival. Granted, he needed Papyrus to give him assistance on more than one occasion, setting up furniture, gathering appropriate baby clothes, but most importantly was the need to share magic with him to help the growing soul.

Sans continued to work as a sentry even to the final days, denying to take any leave until the child had arrived. Besides, despite having multiple jobs, he found ways to still get the job done while not having to do too much at all. Granted, there was a challenge added with not using his magic, but it was all still manageable.

Until that human showed up...

Sans recalled upon his promise to the old lady behind the door, remembering how she seemed to have so much faith in him, someone she’d never met face-to-face with, to keep said promise. When he saw the human pass through, he decided to hold up with the promise, and he would have to make a good first impression with this human if he was to keep an eye out for them.

And what better way to break the ice, than with a joke?

He had the whoopie cushion hand gag rearing to go, and once it was pulled off by the human turning around and shaking his hand, Sans grinned widely as he awaited for the reaction he would get from this kid.

Though despite that, there was no reaction whatsoever from the child. No twitch of the eyes or movement of their mouth.

They were absolutely vacant.

The awkward silence Sans received simply made him cringe, “g _ee lady, you really know how to pick ‘em, huh...?_ ”

This really should have been the red flag for what was to come.

Fast forward: the dog sentries of Snowdin were dusted and long gone, his brother was struck down despite trying to be the brave soul to help the human, Undyne even with all her strength and determination could not stop this small hellion, the Royal Guards in Hotlands, Muffet hardly stood a chance, and Mettaton with even his Neo form only made it easier to become a walking target.

So many monsters had to run away, those who began to hear the terrible news of the human coming their way began to flee to evacuate places and stay clear out of the path. Many hiding away for fear, begged for mercy, mourned the many that were laid to waste.

The human’s final destination was to go straight for the King. And if the King were to die, all the hopes and dreams of monsters ever seeing the light of day would be long lost and no more.

Sans knew he could no longer wait for the next step, he had to confront them himself.

Ever since the human came here, he had never let up to them that he was currently with child. His coat was kept closed and it did a good job to mask his large protruding belly, making it slope more to look like he was just big boned, heck most monsters didn’t know he was expecting either. He only let close family and friends know of this, not out of particular embarrassment, but he was genuinely too lazy to tell everyone. If someone asked, yeah he would admit it, but it did not seem to really matter to announce it to everyone he knew. Sometimes he would just forget he was pregnant at all.

Right now, he was far more aware of it than ever.

With all the nervous tension and the worries in the back of his head, he felt the small forming soul translate an equal amount of anxiety by being active and giving many “kicks”. Sans paced to not only calm his own nerves, but hopefully bring comfort for the growing soul, last thing he needed was for anything to come of them.

He was mentally preparing himself, he would have to use his magic to fight the human, only one of them would leave this hallway alive, and he was determined to make it him. Not just for the sake of all monsters, not just for the sake of the king, but for also the sake of his unborn child. If he threw out a strong attack out the gate, perhaps this could end quickly.

Footsteps echoed from the opposite end of the hallway, Sans composed himself within the few seconds he had and stood there awaiting for the human. He was about to speak when he saw their face: they were _mad_. No, seething with frustrating anger it seemed.

Looks like Sans was correct to assume the human had been using “save points” to restart fights. By this point, they looked fed up and completely infuriated. It might not really be much use in rattling off a speech if they probably had heard it several times over.

“ _let’s just get to the point._ ” Sans said, without hesitating he took hold of them and threw them down.

The human was quick to react and hopped back up before bones would stab at them, Sans then tried flinging them across the room, though they were careful and avoided all the bones to be in the way, lastly Sans brought down gaster blaster heads, and yet this human managed to jump out of the way, anticipating which blasters would come _next_. Once finished, Sans already found himself out of breath, this was meant to make it easier to take down the human, not to make it easier to be taken down himself.

“oh boy, here we go.” Sans groaned, knowing that this changed everything.

Despite all that Sans threw at the human, they were one step ahead, it was more like they had been choreographed in dodging all of his attacks, they even got cocky and tried to throw in some heel turns and dramatic poses, all in mock of him. When they swung that knife, Sans was quick to jump aside, the human even was purposefully lazy in some of their swings as they knew they wouldn’t land a hit. Just how far had this human come to slack off when they had the _opportunity to hit him_? It certainly got harder and harder to keep his own poker face during the fight.

After each attack, he felt his magic deplete more and more, growing more tired and even beginning to ache. Just how could he stop them? If he could not even land a single hit himself.

And oh, real mature, that brat called a human is yawning as they duck under gaster blasts. Could this get any worse-

“a _h!_ ” Sans felt a jab of pain hit his gut, but once he saw the knife swing at him, he was quick to jump out of the way. The mild distraction was not about to stop him.

He threw more bones once again, not landing a single hit.

 _kid just give up already, come on please_. Sans pleaded in his mind, but after his attack failed once more, he felt another breath taking pain strike him. The skeleton began to sweat, beginning to fear the worst for what was happening to him...

These pains were not ordinary cramps, they were far removed from that. These had to be _contractions_.

It was Sans’s turn to throw an attack back, but he stopped, the pain burdening down on him and making him almost unable to move as he feared if he took another step his legs would give out. This obviously piqued the human’s interest as they were curious to what was taking so long for the next move.

“... h-hey...” Sans said out loud, the human tilting their head in response, “... what’s that?” he pointed.

The human frowned, but took to looking over anyway, unknowingly they were immediately thrown and tossed at bones, they got hurt by them, but saved themselves from being completely impaled. It was worth a shot, but Sans could not do much more.

“w-wait, please, just... just hold on a second...” his knees quaked as he hugged at his rounded belly, the human glaring at him harshly, “please... i... i’ll just get down to it: why fight when we can be friends, yanno? buddy, pal... you don’t have to do this, we can just make it easy and you can just... lay down your weapon. start a new, clean your slate, it doesn’t- _mhh_ -it doesn’t have to be like this...”

The human’s glare dissolved into a look of concern, not at all what Sans expected to elicit out of them. Though their face of concern turned to horror as tears welled up in their eyes. 

 _whoa, didn’t think i’d strike a chord like that with ‘em_... Sans knew he was setting them up for a trap, and it looked like it would work out actually, that if they would come close enough he could actually pull it off and take them out in one go.

“ _S-sans?_ ”

The skeleton tensed up and froze, something about how the voice cracked in desperation, got him in a bind.

“O-oh n-no I... N-n-no I’m s-so s-sorry...” the human dropped the knife, letting it clatter to the floor.

Sans breathed through his clenched teeth, putting on a pained grin on his face, “hey, see? wasn’t too bad, r-right? now c’mere an--” before he could say anymore, he felt struck with another contraction, catching his breath and having him fall to his knees.

“Sans!” the child cried out, rushing to him in concern.

“ **don’t you dare come close to me!** ” Sans held up a hand and threatened the human with his glowing eye, catching them off guard and making them step back. Seeing them step away, his hand retreated back down to his abdomen and he breathed heavily, sweat beading at his head and dripping down off his jaw.

“Sans, what’s the matter?”

What the heck was this kid doing, first they show up with all this nerve and ambition to have the skeleton dead, now they were caring for him? He was vulnerable, nothing stopped them from picking up their weapon and ending it right now. Sans felt like he was just awaiting for it to happen.

“Should I get Dr. Alphys? D-do you need me to get help?”

... Was this some sick joke? Granted their voice sounded genuine, but moments ago this kid was swinging a knife as if he was a piñata. They were acting as if none of what was previously going on had happened.

“Sans??”

“ **just do it, alright? you don’t need to patronize me like this.** ” Sans growled, mostly as he was trying to cope with the pain, “ **what are you waiting for?** ”

The human gingerly stepped forward to Sans, and even when he seemed like he was asking for it, he still scooted back away. Then the human knelt down in front of him, and when he took another look at them, they seemed... Different.

They were not at all trying to hurt him or mock him, they truly were showing him mercy. To think, he was about to take them and stake bones through their fleshy body, he could not think to do that now with how they seemed like a whole different person.

Perhaps even the worst of people can change?

“Can I help?”

Sans gulped, he was a mess of panting and sweating, thinking it over he decided that he might as well take this mercy he was being shown and reluctantly nodded.

“y-yeah... i’m gonna need it...”


	2. Because somehow people wanted more?

**Notes for the Chapter:**

> I'm not too happy with how I wrote the last chapter, but whatever, it's all I have to work with and I might as well. Also, I'm sorry if this turns out to be disappointing, it's been a while and I am finally just wrapping this up, so yeeaah.

_"...buddy, pal... you don’t have to do this, we can just make it easy and you can just... lay down your weapon. start a new, clean your slate, it doesn’t- **mhh** -it doesn’t have to be like this..._”

Ready to strike, but hesitating, something within the human's clouded soul seemed to shine through like a beacon: Mercy him. Show mercy. Spare. Mercy. _Mercy._ It was enough to break through this darkened soul, and suddenly standing there in the room before the skeleton was a whole different human.

Sans could see the change in attitude clear and plain as day on the kid's face, as they slowly were making the horrifying realization just what was happening while they were trapped under those dark spells of something that had taken control over their body and soul.

“ _S-sans_?”

They saw the dust on their sweater, sleeves, knees, hands.

“O-oh n-no I... N-n-no I’m s-so s-sorry...” the weight of the knife felt heavy, they mindlessly just let it drop to the floor and the clattering echoed in the hall, lingering a second or two after it finally settled on the ground. The human was unable to fully comprehend just what it was they had done, everything was a blur to them and they felt close to the edge of crying.

“hey, see? wasn’t too bad, r-right? now c’mere an--” Sans began to speak, but the way his face blanked and he dropped to his knees, the child was quick to see that something was now wrong with Sans. Oh no, did _they_ do something to him?

“Sans!” They tried to hurry to his side, only to be warned back by Sans throwing up his hand and flashing his eye, now that was new.

“ **D** **on’t you _dare_ come close to me!** ”

The child did stand back a moment, a little hesitant to approach Sans any closer. He then took his hand back down to rub over his belly and breathed heavily, he looked to be in pain, but there was nothing noticeably wrong.

“Sans, what’s the matter?” they asked, getting no response from him, “Should I get Dr. Alphys? D-do you need me to get help?” he seemed to just avoid looking their way at all, “Sans??”

“ **just do it, alright? you don’t need to patronize me like this. **what are you waiting for?**** ”

Whatever it was that they did, Sans certainly wanted nothing to do with them by this point. Though even if he wanted none of the kid's help, they were ready to insist and take whatever backlash they deserved in order to help and try to make things right... If that was even an option by this point.

Coming closer and kneeling down before him, even as he resisted away, they tried to show that they were not here to harm him, “Can I help?”

After a moment to let it sink in, Sans swallowed hard and nodded, “y-yeah... i’m gonna need it...”

 

♡♥♥♥♥♥♡

 

Wait no, this would be a terrible idea. Asking a 10... _7_.... _8 year old_ - _something whatever_ -a child to help deliver a baby? That would spell disaster... If Sans was to get through this, he would at least need another adult. Though all other monsters were either evacuated or... _dust_... Yeah, he was still having to stomach the fact that bits of dust clung to the child's fabric-hell there seemed to be some _in their hair_.

There was one other monster that resided this far back into the castle.

"A-Asgore..." Sans mustered out, "G-go... Go get him."

The child stood up and seemed to look conflicted, looking back and forth at Sans and the doorway, "Will you be okay?"

"I'll... Manage." Sans said, "Get goin', hurry!"

The human sprinted off, leaving the hallway and their footsteps fading off down the connecting corridor.

 

♥♡♡♡♡♡♥

 

Running as fast as they could be carried on their feet, they reached the throne room, "Asgor-" then to trip on a vine and face plant right into the floor, this startled the gentle giant king, flinching as he looked over his shoulder to see the child lying face down in his flowers.

"Goodness! Why... Who are-"

"Asgore!" They whipped their head up and scrambled to their feet, " _Sans_! Sans needs help! Please hurry, _please_!"

The king sure was confused by all this, a human just runs in, trips into their flower bed, and talks about someone needing help? The child saw his puzzled face and became insistent now that if he would not hurry now, he was prepared to drag him there. The human, in vain, grabbed at the long, flowing, purple cape of Asgore's.

This human child was not like others, something a strange familiarity came from them, it was so hard to place and only left the king to feel some solemn feeling deep down.

"Human, what is the meaning of this?" was all the big fluffy guy could ask.

"Sans! He's hurting! He needs help and I-I don't know who else to turn to!" The child argued, "Please! Just come with me! See him for yourself!"

That was a familiar name too, though it was more a name he recalled from hearing in passing. This just felt too odd, and the more this human pressured him, the more he pondered if it would be wise at all to listen to them. Something felt sorely out of place.

"Hm, alright human, I'll accompany you." If anything, he was planning to keep his guard up, aware of the reports he had heard and knowing very well that there was threats placed on the Underground at the news a human had fallen in and was slaughtering many monsters. What had Asgore confused was that this human did not at all seem like the one from what had been reported. He was awaiting in the throne room for that other human, but instead there is this one? Were there more than one that had fallen down here?

The child began to run up ahead, wanting for the king to hurry, but he took to a steadier pace, ready for anything.

 

♡♥♥♥♥♥♡

 

What took that kid so long? Maybe they just bailed? Maybe the King was trying to kill them? Well, good riddance. Even if he was relying on the human for help, he still resented them quite a bit. You can't just easily forgive someone to have wiped out half the population in the entire Underground, which so happened to include their strongest hero, a beloved celebrity, and most importantly: his only remaining family. Oh Papyrus... What would he say if he was here? Maybe nag him for not keeping in better shape during his pregnancy. Or more fuss over the fact he was using any magic at all during his pregnancy. _But who else would do it?_ he wondered, the King would be struck down and that would be it for ever seeing the sun again.

Ugh, why did it even matter? Sans would never get to enjoy being on the surface without his brother there by his side. Though, it would be unfair to all the other remaining monsters. And to his unborn child. Then again, it was more unfair to his own little souling by even doing what he was doing now.

"I'm so sorry..." Sans choked out quietly, his hand rubbed over his middle.

Quiet footsteps were heard reproaching the room, seems like that human really did come through after all and convinced the king to come and help. Huh, well now wouldn't this be something to write home about, of all the people left in the Underground, and it would be the king who comes to his aid.

"There!" The child exclaiming and pointing at Sans. Finally a connection was made as Asgore looked to see the slumped down skeleton, he trotted over and dropped down by his side. "He's hurting!"

Examining the skeleton and judging by a few factors, Asgore was already jumping to the conclusion. It certainly did not take a lot intuition to guess the source of this pain and strife. A light seemed to click within him, "Sans. How close would you say your contractions are?"

Taking an unsteady breath and shuddering as he breathed out, Sans pondered a moment, he wasn't keeping any time on those things, "U-um... _Not sure_..."

Frowning as Asgore concentrated, he then made a gesture with his hands, deciding against an action halfway through. "Could you please lift up your shirt."

There was a bit of a delay in Sans hearing what he was asked and understanding it, the pain starting to really mess with his head, amongst many other things that swirled around in his skull that made his thoughts swampy and confused. He nodded as he unzipped the jacket and pulled up his shirt, revealing that blue orb of a belly he had. The small, shimmering souling shivered and moved down to the weakest point of the small ectoplasmic membrane.

"Alright, we have enough time."

"Enough ti-"

With no warning, Sans felt two large hands scoop under him like shovels and lift him up. Good grief, he was big! At the very least, he didn't seem to have trouble carrying him despite the extra weight (on a skeleton what even?). Asgore began to march off. The human trailed behind.

 

♥♡♡♡♡♡♥

 

The boss monster had the advantage of being much bigger and having longer legs, his steady march was out rivaling the child that had to run just to keep up. Though the further they got away, the slower the child tried to keep up, losing sight of them by a point as they took a turn and they carried off. It was good now that they helped up thus far, but the more they thought it over... How could they even rectify all this? Even if they, personally, were not to blame, it was still their hands that held that grip on the knife. It was _their_ fault.

" _You just couldn't go through with it, could you_?"

Spinning around to the little voice, the human clutched their sweater and backed away defensively.

" _Or it wasn't you the whole time, was it_?"

The human chewed their lower lip, this little flower, just what was he up to now?

" _... Or was it you_?"

A silent pause.

"... _Ah, nah, it wasn't you, I can tell just by looking at you_." Flowey had a certain edge before, but now it feels to have been ebbed away ever so slightly, " _Nope, a shame though, seeing you slice and dice all those monsters was rather entertaining for a time_."

"P-please no." the child's voice choked up.

" _I was rooting for you back there when you started to get creative in how you swung that knife around, like carving a pumpkin_!"

"Stop it."

" _And yet, here you are, you know if you had just let things take their course, you wouldn't have to be here now to be hearing this. Like how you managed to single handedly take down that big, stingy fish lady from the head of the Royal Guard. Or how you cut that one skeleton's head clean off his shoulders! Oh oh, and kicking that bucket of rusted bolts-though my personal favorite had to be how you ate that old lady's pie and yet still struck her down with one blow!_ "

He gave a maniacal chuckle, soon to see the human running fast away from him, " _Don't worry! It'll all reset eventually!_ "

 

♡♥♥♥♥♥♡

 

Arriving to the small home of Asgore's, the King did not halt once as he immediately took the skeleton to his bedroom, laying him down on the large, actual king size bed. To lay down on something softer and warmer than a cold, polished floor was quiet the relief on Sans's spine. Not exactly comfortable given he still was in active labor, but it was far more preferred than the hallway to the throne room.

Asgore rifled through his armoire as he pulled out old blankets and set them aside. He himself preparing by removing his own formal attire of his armor and practically tossing it aside.

"Y-you do this before?" Sans asked, while carefully adjusting himself on the bed to be sat up instead.

"Somewhat, I was present when my wife gave birth." with the bulky armor set removed, he was a little more nimble as he worked.

"Wh-what about for a skeleton?"

"Can't say I have." The large monster took an old blanket and slipped it under Sans's legs, he had to handle Sans a bit to get the blanket fully under him, which he did not mind much as it just made less work on his own part.

"It's a mess, that much I can say." Sans went back to focusing on his breaths that he took, being a little more mindful to try and even them out and slow them down.

Without evening noticing, the king was already working to remove Sans's jacket, hanging it over the back of the chair that sat in front of his desk, and then he gently pinched the shirt, pulling it up and rolling it over Sans's belly. To which by this point looked like was starting to _melt_. It would be a mere matter of minutes before the whole ectoplasmic midsection would just drop off.

"Alright, everything is set and in place then, please don't mind if you do make a mess, these sheets and blankets are not something I hold dear." Even through something as stressful as this moment, the king was incredible at keeping himself calm and steady, assuring and encouraging. It was truly the only solace out of this entire hell it felt like.

"Would you like to hold my hand?"

Such a generous offer, which Sans opted to decline, "N-no no, I'm good, thank you..."

 

♥♡♡♡♡♡♥

 

Just outside the bedroom, the human had followed in after, though with the door shut they could not enter the room and simply was left to sit out and listen. It gave them more time to reflect on everything that had happened.

This whole setting felt like some nightmare that they just weren't waking up from. How could they do something so cruel to all the people they cared about? Their friends? Their _family_?  Just what the heck was it that possessed them to do such a thing? Would it come back? Was it still even there? The longer they remained here, the more of a threat they felt to be to everyone here. And recalling to the way Sans looked at them, that certainly was not the same skeleton he shared a seat with at Grillby's bar, or the same guy who stacked hotanimals on top their head. And was that all really true what Flowey said? They managed to kill everyone near and dear, and so many other innocent monsters. They felt sick thinking about it, and looking back inside of them, they did see it. They had more LV than they ever have had.

There was no way they could be forgiven by this point, there was no way they could fix this. The only possible solution at all would be to...

 

♡♥♥♥♥♥♡

 

Bearing down, Sans felt his unborn press down at the lowest point of his belly, he grit his teeth tight and gripped the sheets on the bed. He truly lacked the energy to push enough to break through the membrane. The magic around his midsection for months had formed to be practically impenetrable and protect the souling, but now it would have to basically completely shed off as part of the birthing process. Asgore placed his hand to Sans's back, helping support him upright, and the way his large hand curved along with Sans's back felt like the perfect, plush pillow that generated heat too. If he got any comfier, he would probably fall asleep, though that wouldn't do much good with having the contractions keeping him wide awake and aware.

"You're doing good, Sans." the King praised.

Something about the words really helped to ground Sans and give him strength to take a breath before bearing down again, pushing harder than before in the second attempt at breaking the membrane. He gave a strained grunt as he held down and finally let up to take in more air.

With a couple more tries, he took a final breath in and pushed a final time, his face contorting in pain as he let out a whine throughout the duration of it. When the result was a slosh of the ectobelly going from rock solid to suddenly a consistency of jelly in just a second, Sans's body finally slumped back and his head leaned back, taking the time to use any energy he had just to breathe now.

He was gently lied down back onto the bed, all the meanwhile, the king gracefully worked to take care of the now arrived newborn.

"Hello there, yes, hello tiny one." his warm voice greeted, his hands were gentle as feathers when picking the child up from the blue mess, putting them into a fresh blanket that he used to clean off their small body. There were soft little hiccups and whines that Asgore shushed in an warming voice. "Ah, now come say hello to the one that brought you into this world, hm?"

The small body, now swaddled with great care, was placed onto Sans's rising and falling ribcage. He now could get a good look at his newborn: a small skeleton (no surprise there) who appeared to be grimacing at this time. The new parent now tiredly smiled and carefully pat the newborn's back, "Hey kiddo, been one helluva ride, huh?"

 

♥♡♡♡♡♡♥

 

After sometime, Asgore stepped out of the bedroom with soiled blankets in hand, about to carry them off to throw into the wash, he stopped as he saw the human child sat against the wall. Strange, they were still here? Though, where else was there to go, he supposed. Once noticing that there was a near 10 foot monster looming over them, they scrambled up to their feet.

"S-Sa-Ho-Wh-" too many words at once wanted to be said at the same time, "H-how's Sans??"

"Resting and well." Asgore replied, he seemed more blunt than he was when first speaking with him. It must be now that the human was overstaying their welcome, as they could feel a sense of dread creep up their back. "Human..."

The child looked up at the King, it must have been just the place they stood and where the light casted, though Asgore's face appeared darker than before, as if a certain cheerfulness was now gone.

"I cannot say for sure how I feel about you... You do not seem one to be malicious or would have the will to harm others. Yet, among the pollen you picked up in my flowers, I could still see the dust of monsters to you. I don't know the full extent of your crimes, but if anything, you follow right in with the fact that now... Now I must do what is right for the people of the Undergound:

"And that is to take your soul to finally break the barrier."

Standing and staring up at the king, and looking just beyond him to the bedroom and getting a small glimpse of Sans lying on the bed with a bundle nestled closely to his chest in his arms, the human looked the king back in the eyes, and simply nodded.

 

♡

 

Walking passed the door of the Ruins and down the familiar path, stopping in front of the bridge with wide bars on either side of it, there was crunching footsteps approaching from behind, from there a voice soon was heard, "Human."

Without much more direction, the child turned and faced the familiar face, taking his hand-

_-PFFfffffffffttttt-_

"Heh, the old whoopie cushion in the hand trick!"

**Author's Note:**

> I'm sorry I am writing these things. Please don't tell mom.


End file.
